ASR - Acceleration skid control - Cuts back power and uses the ABS system to maintain traction and direction during take off. ASR has gotten better over the years, I think they are on ASR V now or something.
ASD - Automatic locking diff - Its a hydraulic actuated locking differential, which uses a hydraulic pump to activate friction plates in the diff to lock both sides of the diff at low speeds.
SLS - Self leveling suspension - It automatically levels the rear suspension back to the height regardless of how much weight is loaded into the car, within reason of course
4Matic - Should be self explanatory - Like ASR it has also gone under many changes since it debuted and is very different from what it was in the beginning.